1. Field of the Invention
The present invention relates to ethylenically unsaturated, phosphorus-containing, bidentate ligands (monomers) and polymeric derivatives thereof as well as polymeric precursors to said polymeric derivatives and methods of making the same. The present invention also relates to catalyst compositions involving a Group VIII metal in the presence of the polymeric bidentate ligands and use of such catalysts in hydrocyanation, isomerization, and hydroformylation reactions.
2. Description of the Related Art
Phosphorus-based ligands are generally known in catalysis, finding use for a number of commercially important chemical transformations. Phosphorus-based ligands commonly encountered in catalysis include phosphines, phosphinites, phosphonites and phosphites. Monodentate phosphorus ligands, e.g. monophosphine and monophosphite ligands, are compounds that usually contain a single phosphorus atom that serves as an electron donor to a transition metal. Bidentate phosphorus ligands, e.g. bisphosphine, bisphosphinite, bisphosphonite, bisphosphite, and bis(phosphorus) ligands, in general, contain two phosphorus electron donor atoms and typically form cyclic chelate structures with transition metals.
Two particularly important industrial processes using phosphorus ligands as catalysts are olefin hydrocyanation and isomerization of branched nitriles to linear nitriles. Phosphite and phosphinite ligands are particularly good ligands for both reactions. The hydrocyanation of ethylenically unsaturated compounds (olefins) using transition metal complexes with monodentate phosphite ligands is well documented in the prior art. See, for example, U.S. Pat. Nos. 3,496,215; 3,631,191; 3,655,723; 3,766,237 and 5,543,536. Bidentate phosphite ligands have also been shown to be particularly useful ligands in the hydrocyanation of activated ethylenically unsaturated compounds. See, for example, J. Chem. Soc., Chem. Commun., 1991, 1292; J. Chem. Soc., Chem. Commun., 1991, 803; PCT Pat. App. WO 9303839; U.S. Pat. Nos. 5,512,696; 5,723,641; and 5,688,986. Bidentate phosphinite and phosphonite ligands are described in U.S. Pat. Nos. 5,817,850; 5,523,453; 5,693,843; and PCT Pat. App. WO 9964155, WO 9913983, WO 9946044, and WO 9843935.
Hydroformylation is another industrially useful process that utilizes catalysts made from phosphorus-containing ligands. The use of phosphine ligands, including diphosphines, is known for this purpose. The use of catalysts made from phosphite ligands is also known. Such catalysts usually contain a Group VIII metal, as described in, for example, U.S. Pat. No. 5,235,113.
Recovery of the ligand and catalyst is important for a successful commercial process. Typical separation procedures to remove the product(s) from the catalyst and ligand involve extraction with an immiscible solvent or distillation. It is usually difficult to recover the catalyst and ligand quantitatively. For instance, distillation of a volatile product from a non-volatile catalyst results in thermal degradation of the catalyst. Similarly, extraction results in some loss of catalyst into the product phase. For extraction, one would like to be able to select and/or control the solubility of the ligand and catalyst to disfavor solubility in the product phase. These ligands and metals are often very expensive and thus it is important to keep such losses to a minimum for a commercially viable process.
One method to solve the problem of catalyst and product separation is to attach the catalyst to an insoluble support. Examples of this approach have been previously described, and general references on this subject can be found in “Supported Metal Complexes: A New Generation of Catalysts”, F. R. Hartley and D. Boston, Reidel Publishing, 1985; Acta Polymer., 1996, 47, 1; “Comprehensive Organometallic Chemistry”, Ed: G. Wilkinson, F. G. A. Stone, and E. W. Abel, New York: Pergamon Press, 1982, Chapter 55, “Polymer Supported Catalysts”; J. Mol. Catal. A, 1995, 104, 17; and Macromol. Symp., 1994, 80, 241. Specifically, monophosphine and monophosphite ligands attached to solid supports are described in these references. Bisphosphine ligands have also been attached to solid supports and used for catalysis, as described in, for example, U.S. Pat. Nos. 5,432,289 and 5,990,318; J. Mol. Catal. A, 1996, 112, 217, J. Chem. Soc., Chem. Commun., 1996, 653; J. Org. Chem., 1998, 63, 3137; Spec. Chem., 1998, 18, 224 and PCT Pat. App. WO 9812202. PCT Pat. Apps. WO 9906146 and WO 9962855 show use of supported phosphorus ligands in hydrocyanation and hydroformylation reactions, respectively. Bisphosphite ligands have also been grafted to solid supports such as those described in U.S. Pat. No. 6,121,184. The solid support in these prior art examples can be organic, e.g., a polymer resin, or inorganic in nature.
Polymer-supported multidentate phosphorus ligands may be prepared by a variety of methods known in the art, as described in U.S. Pat. Nos. 4,769,498 and 4,668,651, PCT Pat. App. WO 9303839 and WO 9906146, and European Pat. Apps. EP 0864577 A2 and EP 0877029 A2. The prior art discloses side-chain polymers containing multidentate phosphorus ligands as pendant groups.
Another method to solve the problem of separating the catalyst from the reaction product is to copolymerize phosphorus-containing ligands with other non-ligand monomers to produce insoluble phosphorus-containing ligands. Examples of such polymer-immobilized phosphine ligands have been reported in J. Am. Chem. Soc., 2000, 122, 6217 and J. Org. Chem., 1986, 51, 4189. In addition, polymer-immobilized phosphine-phosphite ligands and their use in hydroformylation catalysis have recently been described in Bull. Chem. Soc. Jpn., 1999, 72, 1911; J. Am. Chem. Soc., 1998, 120, 4051; and European Pat. App. EP 0864577.
To address the important issue of ligand recovery, this invention provides novel monomeric bidentate ligands and a method for their synthesis, polymeric bidentate ligands prepared from the monomeric ligands and a method for their synthesis, monomeric or polymeric phosphorus-containing compositions that may be combined with a Group VIII metal, and the use of this monomeric or polymeric phosphorus-containing composition combined with a Group VIII metal to act as a catalyst in reactions for hydrocyanation, hydroformylation, and isomerization. The polymeric, phosporus-containing catalyst composition is readily recoverable from the reaction products.